Method for drying macaroni products



June 20, 1961 R. SAMSON 2,988,819

METHOD FOR DRYING MACARONI PRODUCTS Filed Oct. 24. 1956 Ivar/12"? Zezz Samsorz United States Patent 2,988,819 METHOD FOR DRYING MACARONI PRODUTS Rene Samson, Montreal, Quebec, Canada, assignor to Gebruder Buhler, Uzrnil, Switzerland, a Swiss firm Filed Oct. 24, 1956, Ser. No. 618,074 5 Claims. (CI. 34-31) The present invention relates to improvements in the manufacture of alimentary paste products and more specifically to improvements in the drying operations necessary in manufacturing macaroni products of alimentary paste compositions. The term macaroni products" is intended to cover all varieties of many diiferent shapes of alimentary paste products, for example, long and short macaroni, spaghetti, vermicelli, noodles, alphabets, and

the like.

It is extremely important in the manufacturing process of products of this nature that the finished product be stabilized to withstand handling for packaging, shipping or storage under varying conditions of temperature and humidity with a minimum of breakage even after several days or weeks of storage. This desired result depends largely on the eifective and controlled stabilization of the product during the drying operations.

The drying methods in common use at the present time, in attempting to achieve this desired stabilization necessitate considerable time in the drying and generally require diflicult processes and measures of control which are critical and expensive.

Broadly, the drying procedure involves two main steps, the first of which includes the preliminary drying of the alimentary paste product after it has been extruded into the desired shape from a press, and a resting period under definite and controlled conditions of humidity and temperature. It is' in the preliminary stage of drying that the conversion of protein into gluten, already started during the kneading operations in the press, continues to take place at a faster rate.

The second main step includes a further stage of drying to complete the hydrolysis of. protein into gluten followed by a final dehydration stage. Each of these steps and their intermediate stages must be carried out as mentioned above under controllable and definite conditions of temperature and relative humidity.

The most critical of the steps mentioned, with respect to satisfactory stabilization of the goods, is the second step where the hydrolysis must be completed. The quality of the finished products and the time required to carry out the drying process depends largely on this step, as long as preliminary drying operations have been carried out in the proper and right conditions of drying process. a

It has been-proposed-in the prior art that this step might be accelerated by soaking the extruded product in boiling water'for a short periodof time, drawing the water oh anddrying the product immediately afterwards atahigh temperature. However, this hasnot been too satisfactory in that the resultant product is not stable and the shape of the product is altered and twisted. It should be mentioned that in-addition'to the stability required, it is very important that in the manufacturing ofmacaroni products the shape, as extruded, be maintained during the dryingoperations. Otherwise, the finished products will be diflicult and in fact impractical for the necessary subsequent handling and packaging. To the best of the applicants knowledge, no satisfactory method has yet been proposed for the carrying out of this important drying process in a manner which is efiicient, suitable for application in automatic dryers, and capable of yielding a satisfactory product .with respect to the desired uniformity of shape, stability and quality. e

y The present invention. aims to provide-a method of ice ' to any and all types of drying apparatus and which will yield a product having the desired qualities mentioned.

Briefly, it has been found that a main factor controlling the efiectiveness and speed of the first and second critical drying steps consists in the breaking down of the surface tension of the water in and on the surface of the goods during the entire drying operation and particularly during the hydrolysis stage.

It should be explained that all varieties of macaroni products in the extruded or shaped condition from a press have a moisture content of from about 26% to about 34%. In the preliminary drying stage after extrusion, drying operation is rapid in order to eliminate the excess moisture on the surface of the goods and speed up the hydrolysis and conversion of protein into gluten. It is followed by the resting period to allow the moisture within the goods to equalize all through the mass of the product. In this resting period there is substantially no circulation of air. In this preliminary drying a very high hygroscopic condition with a very high relative humidity above must be maintained using air at temperatures varying between 70 F. to F. depending on the type of dryers used which will remove the excess moisture from the surface of the product. From this first step the products are brought to the second and most important step of this drying process after the percentage of moisturehas been reduced down to from about 17% to 21%, in the macaroni products which means over 60% of the humidity to be removed from the product.

In this step and after the moisture content of the prod.- uct has reached the required level from 17% to 21%, the exothermic reaction which must take place due to hydrolysis of protein into gluten is practically completed. This hydrolysis is not chemically a complete reaction, otherwise the gluten would not retain its elasticity as is necessary for stabilized product. Finally, the products are subjected to further drying stage reducing the moistu-re content to about 14% or'less which means less than 40% of the total moisture to be removed from the product.

As is well known in the art, one of the main difliculties in the drying of macaroni products is that they are non-conductive, thus creating a problem in removing the water evenly and equally from the interior to the exterior of the product. Accordingly, when prior art attempts have been made to achieve the desired acceleration of this important drying process described and the resulting hydrolysis the main idea has been to subject the goods in this second stage to increased temperatures which unfortunately prevented a thorough stabilization of the product and also served to unequally dehydrate the prodnet and set up contraction or stresses which cause the product to break or crack. This latter phenomenon is known in the trade as checking.

-In accordance with the present method the hydrolysis action of the second step can be accelerated and completed by recirculating air through the products which has already passed through the products and therefore contains a percentage of organic matter. It has been found that this old or organic matter containing air has a somewhat catalytic action breaking up and reducing the surface tension of water in and on the products. By the reduction of surface tension the removal of moisture from the products is greatly accelerated which permits the drying operations to be carried out at a relatively low temperature and at the same time speeds up the hydrolysis or conversion of protein to gluten in such a way so as to stabilize the products prior to the final reduction of moisture content to the level required when the products come out of the dryer.

Since over 60% of the moisture is removed from the Patented June 20, 1961 2 p odu n t e p el m na y sta e, it is ve y impo tant and even necessary for maximum results to re-use and recirculated substantially all the air used in the preliminfil'y Stage into the second drying stage because this air contains the highest percentage of volatile constituents of organic matter from the drying products.

More specifically, and in accordance with the present method, to obtain maximum results, from 80% to a preferred 100% of the air circulated in the dryer units is 'old or organic matter bearing air. If percentages as low as 60% to 40% or even 20% are made use of, the drying process requires higher temperature and longer drying time proportionate to the decreasing percentage of recirculated conditioned air used in the process. This air is preferably produced in the dryer by the operational functions of the dryer and is preferably used in all stages of the drying operations.

For example, in an automatic dryer of the type having a first or preliminary stage unit and a single second stage or multiple interconnected second stage units, the air is withdrawn from the front of the second stage units and recirculated back in the first stage unit or preliminary.

It is then circulated through the first stage unit or preliminary and back to the last end of the second stage units where the dried goods are coming out and through all the second stage units back to the front unit of the second stage from there, back into preliminary and so on in a closed circuit. Since in a modern type automatic dryer, the distance from the first stage unit to the last of the second stage units is considerable, about 100 feet or more, when the old air is recirculated through an outside duct it is cooled down from about 115 F. as it leaves the first stage unit, to about 65 F. or substantially room temperature as it re-enters the last of the second stage units. This makes it possible to control the moisture content of the recirculated air directly since if the moisture content of the air becomes too high it will condense partially within the latter portion of the duct and this condensate can be easily removed. If the moisture content is too low, it can be increased by an injection of steam or water spray. If necessary a small percentage of fresh air can be introduced to achieve the desired balance of humidity and temperature. Since the organic matter carried in the air is more volatile than water, it will not condense at the same rate and will thus be carried back into the dryer even if a fairly large percentage of moisture in the circulated air is eliminated as a condensated product.

The advantages arrived at by this method are many and principally that macaroni products thus produced have a uniform shape, excellent colour and texture as well as quality and are completely stable as required for efficient handling and packaging. Since they are dried at relatively lower temperatures and in a shorter period of time than was possible by the prior art methods known the saving in manufacturing costs is considerable.

In order to illustrate diagrammatically one preferred way of carrying out the method of the invention in an automatic continuous flow dryer set-up reference will be made to the accompanying drawing where 10 represents a first stage or preliminary dryer unit through which the macaroni products pass in the first relative rapid drying and resting period which is intended to reduce the moisture contents of the goods down from about the usual 26% to 35% as they come out of the presses to about as they proceed to the second drying stage. The second stage dryer unit indicated at 12 may consist of a single tunnel or any uneven number of courses or interconnected casings depending on the temperatures and the type of air circulating device utilized. During each course the goods are conveyed along a circuitous path and subjected to alternate periods or zones of drying and resting so as to equalize the moisture removal. The drying temperatures are reduced from one course to the next t9 avoid a too high surface dehydration of the products as their moisture content diminishes.

It should be mentioned that long goods are usually dried in installations of this nature while short goods" are usually dried on moving screens in layers of different thickness. The term long goods in the art refers to macaroni products having a length of from about 6 inches or longer. The term short goods is usually applied to lengths of less than 6 inches such as, alphabets, twisted noodles, elbows or the like. It will be ap preciated that while the present method is fully effective in the drying of short goods it is directed mainly to the drying of long goods which as previously explained are considerably more difiicult to handle and require a longer time to dry than short goods.

In the type of automatic dryer unit diagrammatically illustrated conveyor means are provided for conveying the product A through the various drying stages and each unit is provided with controlling means to regulate the temperature and humidity of the air within the units. Ordinarily and using the known standard drying methods, the first unit 10 which removes the major portion of the surface moisture is maintained at from about 150 F. to about 180 F. and the second stage units are maintained at from about 140 F. at the first course down to about 75 F. and sometimes over F. at the last course. In some types of automatic dryers a cooling stage separated from the dryer itself is required.

With the present method the temperature of the first unit 10 can be reduced to about F. and the second unit from about 90 F. at one end to about 65 F. at the other end, while the drying time can also be considerably reduced.

To efiiciently carry out the present method in the apparatus shown, and by way of illustration, a first conduit or duct 14 is provided which connects the second stage casing 12 to the first stage unit so that air is drawn from the unit 12 adjacent the first course and delivered to the upper portion of the unit 10. A valve or damper 18 is also provided whereby the duct 14 can be closed off. If a small percentage of fresh air is required, valve 28 can be opened. A heater 30 can be made use of to increase temperature of the air.

A second and elongated duct 20 extends from the front and upper portion of the second unit 12 to the last course or end of the combined units 12 so that the air when circulated through the unit 12 against the conveying course of the goods is recirculated back to the first stage of the drying operation, by means of fan 36 through duct 14. This air passes through the unit 10 and is again withdrawn by the duct 8 forming a substantially closed circuit. A fan or blower 16 is connected into the duct 20 to cause a circulating air stream. Fan 16 is placed at front end of second stage to permit recirculation of air from front to back end of unit 12 when preliminary dryer is closed down, for example when the extruding or forming press is stopped and dryer is being emptied for shut down.

A further duct 22 is provided on the first stage unit 10 and serves to draw the air through the duct 8 from the bottom of the unit and recirculate it through the top of the unit thus forming a separate closed circuit for the first or preliminary drying stage. A valve or damper 26 is provided so that the duct 22 can be closed 01f in normal operation.

The reason for the separate circuit created by the duct 22 is that in starting up the dryer, and in order to provide the required old or organic matter bearing air, the first stage unit is operated as a closed circuit until the goods have passed through the preliminary drying and resting. For this purpose the duct 14 is closed off and the duct 22 opened, duct 8 is also closed from the duct 20 with damper 38 so that the drying air within the unit is recirculated by the fan or blower 39 through the goods andbecomes old or organic matter bearing. Once the goods are ready to pass into the second drying stage the duct 22 is closed off, damper 38 is opened and the duct 14 opened so that the organic matter bearing air is recirculated through the entire second stage unit and is now withdrawn from the second stage by the duct 14 and recirculated back through the first unit 10. Air from unit is drawn back into 12 by fan 16 through duct 8.

As previously mentioned, since the duct 20 is an exterior duct and of a considerable length, in the order of 100 feet long, the air passing along'the duct is cooled say from about 115 R, which is the operating temperature of the first unit 10 under the conditions of the present method, down to about 65 F. or approximately room temperature at the far end as it enters the unit 12. This heat exchange or cooling effect makes it possible to maintain the interior temperatures of the units 10, 12 at the desired controlled degree without the necessity of providing additional temperature and humidity controls beyond those generally required in apparatus of this nature. If the recirculated air becomes too wet and condensation occurs in the cooling along the duct 20 it is a simplematter toprovide a condensate trap or the like. If the humidity rises beyond a required predetermineddegreeQa small percentage of fresh air can be introduced from a controlling point 41 controlled by a damper 42 and connected into the duct 20. It is preferable, however, not to draw fresh air into the duct. Cooling the air in the duct with a refrigerating device of some kind is more desirable so as to maintain the highest possible percentage of organic matter in the air.

If it is necessary to raise the humidity of the recirculating air, steam or a water jet can be injected at the control point. Since these expedients are well known in the art and do not form part of the invention, it is not thought necessary to describe or illustrate them in detail. On duct 20 a trap 32 is provided to let a percentage of air out of the duct if the pressure is too high. The trap door 32 is controlled by a weight equivalent to pressure required to open it.

With automatic dryers known controlling apparatus can be made use of in any stage of the drying process of the invention to control the air circulation, its volume, speed, temperature, relative humidity, volume of recirculated air, as well as its percentage of organic matter, intake of fresh air. In this way a drying apparatus adapted to carry out the invention can be made fully automatic to compensate for and control in all respects the diiferent factors involved in the drying process whether it involves single or multiple drying stages.

It will be understood that the apparatus or dryer form used to carry out the present method may be varied to suit particular requirements. The main factors which must be maintained for the most efiicient and continuous carrying out of the present method are that the old or organic matter carrying air described must constitute a major portion of the drying air recirculated, from about 80% to a preferred 100%; the recirculating circuit must be a closed circuit to maintain the required high percentage of organic matter bearing air; the organic matter bearing air should be initially withdrawn from and subsequently recirculated through the first drying stage since due to the higher temperatures and initial moisture content of the goods at this point approximately 60% of the moisture content is withdrawn from the goods and consequently the air more fully charged with the desired organic matter.

These conditions are essential since this organic matter present in the air of very high relative humidity is responsible for the catalytic action of the recirculated air in a closed circuit to stabilize the goods, complete the hydrolysis of protein into gluten and speed up the drying operation so that it is completed in a shorter time, and at lower temperatures.

The use of this conditioned air throughout all drying stages permits the drying atmosphere to be ideally conditioned with the highest relative humidity, from 85% to %,3t the lowest temperatures from about F, to'about :65 F. Under such conditions," hydrolysisof protein to gluten is accelerated, which permits the desired even drying of the macaroni products to be accomplished in considerably less time than has been possible with the known drying methods. For example, normally in conventional dryers and depending on their particular arrangement, it takes between 30 to 60 hours to dry long goods. In some types of automatic continuous dryers it has been claimed that the drying time has been reduced to between 18 and 36 hours depending on varieties of macaroni products to be dried. Using the present method drying times for all varieties of macaroni products have been reduced, in automatic dryers, down to 15 hours or less depending on the variety.

While, as previously mentioned, the old or organic matter bearing air is preferably drawn from the drying apparatus, it is also contemplated that conditioned air for recirculation having the desired organic matter bearing qualities might be produced by other means. For example, the organic impregnation of the air might be accelerated chemically outside of the dryer and introduced as required. i

For example, this organic matter can be obtained artificially by treating wet dough in an excess of water to obtain an uncompleted fermentation. This water containing organic matter can then be used in any desired drying stage by means of a spray or any other mechanical device. While the exact composition is not known, it is believed that the organic matter is a breakdown or exudation product of the alimentary paste through partial fermentation of the wheat starch and by partial hydrolisation of protein to gluten.

As previously mentioned, the drying process as explained above comprises two very important stages of drying. In the first stage preliminary drying, there are two steps, one of fast drying followed by a so-called sweating period. In the latter, of course, there is no air circulation and during the equilibrium of moisture in the product before final drying stage, there is a certain percentage of volatile organic matter and moisture which is free from the product and helps to a certain extent, but in a very small way, to facilitate the drying operation.

Consequently, it is possible to devise a unit comprising only one stage in which could be combined the preliminary as well as second stage of drying since sweating operation could be eliminated when making use of a concentration of organic matter which would be in the proportion required to enable and maintain a gradual reduction of moisture in product in proportion required from the front end or entrance of the dryer until the end or the outlet of the unit so as to permit the catalytic action of organic matter to take place gradually and at the same time stabilize the goods to proper consistency and obtain a finished product of very good quality.

I claim:

1. A method of drying long macaroni products comprising the steps of conveying said products through progressive drying stages in an enclosure in the presence of heated air having a humidity content of about 85%, supplying conditioned air within said enclosure impregnated with volatile constituents of organic matter from said products by passing air through said products in a closed circuit in a first stage of said drying process at temperatures of from about 110 F. to about F. and a humidity content of about 85%, recirculating at least a portion of said conditioned air so supplied from said first stage in a closed circuit through said products in a further stage of said drying process at temperatures from about 65 F. to about 110 F. and at a relative humidity of about 85%, and bleeding off air from said further stage conditioned with volatile constituents of organic matter from said products and mixing said conditioned 7 air with the air circulated in said first stage, whereby said conditioned air is passed through saidproducts during said drying process and is adapted through catalytic ac tion to afiect the surface moisture on or in said products accelerating the moisture removal therefrom.

2. A method of drying long macaroni products, as claimed in claim 1, wherein said conditioned air is maintained at from about 80% to about 100% of the total air circulated within said drying enclosure.

3. A method of drying long macaroni products in progressive drying stages in a drying enclosure, comprising the steps of conveying said products through a first drying chamber, recirculating air through said chamber in a closed circuit at about 85% relative humidity and at temperatures of from about 110 F. to about 130 F., conveying said products through a second chamber, recirculating air through said second chamber in a closed circuit at about 85 relative humidity and at temperatures of from about 65 F. to about 110 F., bleeding off air from said first chamber conditioned with volatile constituents of organic matter from said products and mixing said conditioned air with the air circulated in said second chamber, whereby said conditioned air is circulated through said products during said drying stages and i's adapted through catalytic action to etfect the surface moisture on or in said products accelerating the moisture removal therefrom. I

4. A methodof drying long macaroni products, as claimed in claim 3, including the step of bleeding off air from said second chamber and mixing it with air circulating insaid first chamber.

5. A method of drying long macaroni products, as claimed in claim 3, wherein said conditioned air is maintained at from about to about of'th' total air circulated within said first and second drying chambers. t

References Cited in the file of this patent UNITED STATES PATENTS 686,677 Mahoudeau Nov. 12, 1901 1,305,599 Goubert June 3, 1919 1,445,011 Fontana Feb. 13, 1923 1,822,313 Quiggle et al Sept. 8, 1931 2,259,963 Surico Oct. 21, 1941 2,466,130 Surico Apr. 5, 1949 2,732,627 Fava Jan. 31, 1956 

